Copper-titanium-silicon alloys



described, develop remarkable hardness and.

Patented July 13, 1937 UNITED STATES.

PATENT OFFICE oorPEa TirAmuM-smoon' ALLOYS George F. Comstock, Niagara Falls, N. Y., assignor to The Titanium Alloy Manufacturing Company, New York, N. Y., a corporation of Maine No Drawing. Application May 1'7, 1935 Serial No. 21,983

' 10 Claims.

trical conductivity, particularly in respect tothese ternary copper alloys in the form of castings.

Heretofore various copper alloys have been temper-hardened by being cooled from high temperatures ranging from 650 to 1000" C. and subsequently annealing same at, relatively lower temperatures, say from 250 C. to 500 C., for a period of time inversely proportionate to the annealing temperatures used.

It has been found that such temper-hardening heat treatments of binary as well as ternary copper alloys impart increased hardness, strength and electrical conductivity to the resultant alloy, but also that generally the presence of a third element in addition to copper and titanium materially reduces the electrical conductivity of the heat-treated alloy below the value characteristic of the heat-treated copper-titanium alloy with out the third element.

I have discovered, as a result of my experiments andtests, that ternary copper-titaniumsilicon alloys, provided the amounts of titanium and silicon are kept within very definite proportions, which alloys are then subjected to the temper-hardening heat treatments that I have strength together with surprisingly good electrical conductivity in the form of castings. While the use of titanium and silicon as components of copper alloys is known with the maximum tita-. nium content up to four per cent and up to five per cent of silicon, such ternary alloys when subjected to heat-hardening treatments have been found too high in electrical resistance for conducting purposes.

On the contrary, I have discovered that copper-titanium-silicon alloys having a titanium content between 0.40 per cent and 1.03 per cent and a silicon content from 0.03 percent to 0.59 per cent, particularly in the form of copper alloy castings, develope when heat-hardened certain.

mechanical and electrical properties that are entirely different from the binary copper alloys in which titanium and silicon are separately alloyed with the copper, and also from the ternary ranges I have found to be especially adapted to impart good electrical conductivity.

For example, in the form of castings, I have found agood combination of the desiredhardness, strength and electrical conductivity in improved heat-hardened copper-titanium alloys with the addition of silicon not to exceed 0.60 per cent with the silicon content always lower than that of the titanium. Such improved copper-titanium-silicon alloy castings that I have developed and tested after heating two hours at about 1650 F. followed by quenching in water and reheating for 24 hours at about 850 F. possessed the following mechanical properties:

Rockwell hardness E 79 to 91 1 Yield point 1bs. per sq. in 20, 000 to 30, 000 Tensile strength do 35,000 to 45,000 Elongationn 7 to27 composition of titanium and silicon according to the following table that represents various tests as to electrical conductivity that I have made on alloys tempered for maximum hardness and strength;

Electrical conductivity after quenching and tempering Titanium content Silicon content From this series of tests, I found that the best electrical conductivity in these coppertitanium-s'ilicon alloys heat-treated for maximum hardness was obtained with 0.50 to 0.85 per cent titanium and 0.23 to 0.40 per cent silicon with the balance substantially copper. My preferred ternary copper alloy casting containing 0.65 per cent titanium and 0.35 per cent silicon with the balance copper had electrical conductivity from 40 to 47% as so heat-treated, slight variations in this percentage of conductivity being due to the presence of small amounts of impurities, and differences in foundry practice.

I also found fromthese tests that copper-titanium-silicon alloys outside the critical range I have given (0.50% to 0.90% Ti and with 0.20% to 0.45% Si) with either more or less titanium and with either more or less silicon were appreciably lower in electrical conductivity. In none of my improved ternary copper-titanium-silicon alloys does the titanium and silicon content exceed one and one-half per cent of either metal alloyed with the copper.

Hence the essence of my discovery resides in those heat-treated copper-titanium silicon alloys, preferably in the form of copper castings, that contain appreciable amounts of silicon not to exceed 0.60 per cent, along with the titanium content not tb exceed 1.50 per cent, which titanium content is always greater than that of the silicon, such ternary copper alloys having improved mechanical properties as well as good electrical conductivity due to the combined effects of the titanium and silicon on copper when their respective contents are confined to the definite proportions shown in the foregoing table.

By microscopic examination of samples of copper alloys containing about 0.8% titanium and 0.3% silicon, both as cast and after heat-treatment, it was indicated that an intermetallic compound, probably a titanide or titano-silicide of copper, was caused to dissolve partially in the copper matrix during the high-temperature treatment, and held to some degree in solution on quenching. The alloy with some of the compound in solution was in acomparatively soft condition, having a Rockwell hardness number of about 50 on the E scale, andhad comparatively low electrical conductivity, of about 25%.

The subsequent tempering treatment consisting of heating at 850 F. for 24 hours then caused the dissolved intermetallic compound to precipitate more uniformly in fine particles, so that the copper matrix was stiffened against deformation by the presence of the fine particles of hard compound, and its electrical conductivity was markedly improved by the removal of titanium and silicon from solid solution. The hardness after tempering was thus about 82 Rockwell E and the electrical conductivity about 41%.

' The useful effect of silicon-in these copper-titanium-silicon alloys, in the proportions forming in part the substance of my invention, seems to consist inthe lower solubility of the titano-sili cide, as compared with the titanide free from sili-' con, in the temper-hardened copper alloy, so that on account of the presence of the correct proportion-of silicon in the alloy, the precipitation of of silicon is lacking. However, if too much silicon is present, the'excess is not precipitated with the titanium compound, and the conductivity is again less, as is also indicated in this table.

The heat-hardening temperatures which I preferably use to obtain the best results vary considerably with the size of the parts and character of the alloy so treated and in some castings the quenching treatment may be omitted, and only the'tempering heat-treatment used, without excessive impairment of the desired properties in the final product. This feature is illustrated in.

the table of results presented in the example below marked A. If the maximum hardness and strength are not required .in castings of my new copper-titanium-silicon alloy, they may be tempered at higher temperatures than the best for strength and hardness, with very much improved electrical conductivity. For instance, by tem-' paring the alloy mentioned above, containing about 0.8% titanium and 0.3% silicon, at a temperature 150 to 200 F. above the standard tempering temperature of 850 F., and cooling slowly in the furnace, electrical conductivity of over 62% was attained, but with Rockwell hardness alloy was melted in a graphite crucible under a glass flux. The crucible was heated by oil. After superheating to about 2536 F., the copper was deoxidized with 2% pounds of a siliconcalcium-copper alloy, and 5'pounds ounces of silicon-copper were then added to the melt and stirred in. After 5 minutes further heating the glass flux was removed, and 3 pounds of metallic titanium were added by means or inverted graphite cups (known as phosphorizers") which served to keep thetitanium submerged in the copper and away from the air until dissolved. The crucible was then withdrawn from the furnace, skimmed, and poured in about five minutes after the titanium addition. The analysisof this heat was 0.87% titanium, 0.35% silicon, l

and 0.04% iron with the balance copper.

Test bars about 16 inches long and inch in Electrical Rockwell Condition of test-bar conductiv- E ity hardness Percent As cast, roughly filed and polished 27. 3 Tempered 24 hours at 850' 36, 0 Heated 2 hrs. at 1650 F. quenched in water 26. 9 Qnenched as above, tempered 24 hrs. at 850 F. and air cooled 40. 1

Tempered further at 950 F. for 24 hrs. and slowly cooled 46.5 Tempered further at 1050 F..for 24 hrs.

and slowly cooled 71. 4

Castings previously used for the electrodeholder part such as was poured from this heat were generally of two kinds, namely either pure assess E, has only 18 to 20% conductivity so that Z and particularly since it possesses a better combination of hardness and electrical conductivity when compared with the alloys previously used for castings.

I claim as my invention: 1. A heat-hardened copper-titanium-silicon alby containing not to exceed one and one-half per cent of titanium and less silicon than titanium with the balance substantially copper; said alloy having electrical conductivity over 35%. Rockwell hardness above 65 E and a yield point of at least 17,000-pounds per square inch.

2. A heat-hardened copper-titanium-silicon alicy-casting containing not to exceed one and onehalf per cent of titanium and less silicon than titanium with the balance substantially copper; said alloy having electrical conductivity over 35%, Rockwell hardness above 65 E and a yield point of at least 17,000 pounds per square inch. 3. Aheat-hardened copper-titanium-silicon alloy containing not to exceed one and one-half per cent of titanium and not to exceed 0.60 per cent of silicon with the balance substantially copper; said alloy having electrical conductivity over Rockwell hardness above. 65 E and a yield point of at least 17,000 pounds per square inch.

4. A heat-hardened copper-titanium-silicon alloy casting containing not to exceed one and onehalf per cent of titanium and not to exceed 0.60 per cent of silicon with the balance substantially copper; said alloy having electrical conductivity over 35%,. Rockwell harness above 65 E and a yield point of at least 17,000 pounds per square inch. i

5. A heat-hardened copper-titanium-siiicon alloy casting containing titanium between 0.40 per cent and 1.03 per cent, siliconbetween 0.03 per cent and 0.59 per cent with the balance substantially copper; said alloy having electrical conductivity over 35%, Rockwell hardness above E and a yield point at least 17,000 pounds per square inch.

6. A heat-hardened copper-titanium-silicon alloy casting containing titanium from 0.50 to 0.90 per cent, silicon from 0.20 to 0.45 per cent with the balance substantially copper; said alloy having electrical conductivity over 35%, Rockwell hardness above 65 E and a yield point at least 17,000 pounds per square inch.

7. A heat-hardened copper-titanium-silicon alloy casting containing titanium about 0.65 per cent, silicon about 0.35 per cent with the balance substantially copper; said alloy having electrical conductivity over 35%, Rockwell hardness above 65E and a yield point at least 17,000 pounds per square inch.

- 8. A heat-hardened copper-titanium-silicon alloy casting containing approximately 0.87 per cent titanium, 0.35 per cent silicon, 0.04 per cent iron with the balance substantially copper; said alloy having electrical conductivity above 35 per cent and Rockwell hardness above 65 E.

9. A heat-hardened copper casting formed of an alloy containing titanium from 0.50 to 0.90 per cent, silicon from 0.20 to 0.45 per cent with the balance substantially copper, having electrical conductivity of at least 40%, Rockwell hardthe balance substantially copper, having electrical conductivity of at least 40%, Rockwell hardness over E produced by a heat treatment consisting of heating said casting to about 1650 F. for about 2 hours, then quenching same in water, and then tempering the casting at about 850 F. to 1050 F. for 24 to 48 hours.

GEORGE F. coMs'rocK. 

